JP2008241412A - Radiation image conversion panel and method for manufacturing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a radiation image conversion panel which is excellent in luminance and sharpness in itself. <P>SOLUTION: The method for manufacturing the radiation image conversion panel includes: the process (A) of mixing phosphor materials; the process (B) of taking them into a resistance-heating crucible to condition of the moisture of them; the process (C) of mounting the resistance-heating crucible on an evaporator and forming a phosphor layer on a substrate through evaporation; and the process (C) of forming a protective film. The method is characterized in that a mixture made by mixing a compound expressed by a general formula (1), M<SP>1</SP>X. aM<SP>2</SP>X' . bM<SP>3</SP>X" :eA, and a Europium compound is used as a phosphor material and in that the relative humidity in the process (B) is set at 3 to 40%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a radiation image conversion panel using a photostimulable phosphor and a manufacturing method thereof.

  Radiation images such as X-ray images are often used in fields such as disease diagnosis. The X-ray image is obtained by irradiating the phosphor layer (phosphor screen) with X-rays that have passed through the subject, thereby generating visible light, and then using this visible light as when taking a normal photograph. Thus, a so-called radiographic method in which a silver halide photographic light-sensitive material (hereinafter also simply referred to as a light-sensitive material) is irradiated and then developed to obtain a visible silver image is widely used.

  However, in recent years, a new method for taking out an image directly from a phosphor layer has been developed instead of an image forming method using a photosensitive material having a silver halide salt. In this method, after the radiation transmitted through the subject is absorbed by the phosphor, the phosphor is excited by light or thermal energy, for example, so that the radiation energy accumulated by the phosphor is absorbed as fluorescence. There is a method of emitting and detecting this fluorescence and imaging.

  Specifically, for example, a radiation image conversion method using a photostimulable phosphor as described in US Pat. No. 3,859,527 and JP-A-55-12144 is known. Yes. This method uses a radiation image conversion panel using a stimulable phosphor layer containing a stimulable phosphor, and the radiation transmitted through the subject is applied to the stimulable phosphor layer of the radiation image conversion panel. , By storing radiation energy corresponding to the radiation transmission density of each part of the subject, and then exciting the stimulable phosphor in time series with electromagnetic waves (excitation light) such as visible light and infrared light. Radiation energy accumulated in the body is emitted as stimulated emission, and a signal based on the intensity of this light is photoelectrically converted to obtain an electrical signal, and this signal is used for recording materials such as photosensitive materials, CRTs, etc. The image is reproduced as a visible image on the display device.

  According to the above radiographic image reproduction method, a radiographic image with abundant information can be obtained with a much smaller exposure dose as compared with a radiographic method using a combination of a conventional radiographic film and an intensifying screen. Has the advantage.

  Radiation image conversion panels using these photostimulable phosphors, after accumulating radiation image information, release accumulated energy by scanning excitation light, so that radiation images can be accumulated again after scanning and used repeatedly. Is possible. In other words, the conventional radiographic method consumes a radiographic film for each radiographing, whereas this radiographic image conversion method repeatedly uses a radiographic image conversion panel. It is advantageous.

  Further, in recent years, a higher-definition radiation image conversion panel has been required for analysis of diagnostic images. As means for improving the sharpness, for example, an attempt has been made to improve the sensitivity and sharpness by controlling the shape of the photostimulable phosphor to be formed.

  As one of these attempts, for example, from a fine pseudo-columnar block described in JP-A No. 61-142497, which is formed by depositing a photostimulable phosphor on a support having a fine concavo-convex pattern. There is a method using a stimulable phosphor layer.

  Further, as described in JP-A-61-142500, a crack between columnar blocks obtained by depositing a photostimulable phosphor on a support having a fine pattern is subjected to shock treatment for further development. A method using a radiation image conversion panel having a photostimulable phosphor layer formed, and a radiation image conversion in which a photostimulable phosphor layer formed on the surface of a support is cracked from the surface side to form a pseudo columnar shape A method using a panel (see, for example, Patent Document 1), and further a method in which a stimulable phosphor layer having a cavity is formed on the upper surface of a support by vapor deposition, and then a cavity is grown by heat treatment to provide a crack, etc. (For example, refer to Patent Document 2).

  Further, there has been proposed a radiation image conversion panel having a photostimulable phosphor layer in which elongated columnar crystals having a certain inclination with respect to the normal direction of the support are formed on the support by vapor deposition (for example, And Patent Document 3).

  Recently, a radiation image conversion panel using a stimulable phosphor activated with Eu based on an alkali halide such as CsBr has been proposed, and in particular, high X-rays that have not been obtained by using Eu as an activator. It became possible to derive the conversion efficiency.

There is also known a technique intended to improve sensitivity by evaporating one or more evaporation sources including a phosphor base material and an activator component such as EuOX or a mixture of EuOX and EuXm in an atmosphere having a predetermined oxygen partial pressure. (For example, see Patent Document 4).
JP 62-39737 A JP-A-62-110200 JP-A-2-58000 Japanese Patent Laid-Open No. 2004-233134

  The objective of this invention is providing the manufacturing method of the radiation image conversion panel excellent in the brightness | luminance and sharpness as a radiation image conversion panel.

  The above object of the present invention is achieved by the following configurations.

  1. Step (A) of mixing phosphor raw material, step (B) of taking the phosphor raw material in a resistance heating crucible and adjusting humidity, installing the resistance heating crucible in a vapor deposition apparatus, and forming a phosphor layer on the substrate by vapor deposition In the manufacturing method of the radiation image conversion panel which consists of the process (C) which forms, and the process (C) which forms a protective film, the mixture which mixed the compound and the europium compound which are represented by following General formula (1) as a fluorescent substance raw material is used. A method for producing a radiation image conversion panel, wherein the relative humidity in step (B) is 3 to 40%.

The general formula ^{(1) M 1 X · aM} 2 X '· bM 3 X ": eA
(In the formula, M ¹ is at least one alkali metal atom selected from Li, Na, K, Rb and Cs atoms, and M ² is Be, Mg, Ca, Sr, Ba, Zn, Cd, Cu. And at least one divalent metal atom selected from each atom of Ni, and M ³ is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, At least one trivalent metal atom selected from each atom of Tm, Yb, Lu, Al, Ga and In, and X, X ′ and X ″ are at least selected from each atom of F, Cl, Br and I 1 type of halogen atom, A is Eu, Tb, In, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, Tl, Na, Ag, Cu and Mg. At least one metal atom selected from each atom, and , B, e each represent a number between 0 ≦ a <0.5,0 ≦ b <0.5,0 ≦ e ≦ 0.2.)
2. 2. The method for producing a radiation image conversion panel as described in 1 above, wherein the relative humidity in the step (A) is 3 to 60%.

3. 3. The method for producing a radiation image conversion panel according to 1 or 2, wherein M ^{1 in the} general formula (1) is Cs and X is Br.

  4). A radiation image conversion panel manufactured by the method for manufacturing a radiation image conversion panel according to any one of 1 to 3 above.

  By this invention, the manufacturing method of the radiation image conversion panel excellent in the brightness | luminance and sharpness as a radiation image conversion panel was able to be provided.

  Hereinafter, the present invention will be described in detail.

  The present invention, the step (A) of mixing the phosphor material, the step (B) of taking the phosphor material in a resistance heating crucible and adjusting the humidity, the resistance heating crucible installed in a vapor deposition apparatus, and the phosphor on the substrate by vapor deposition In the method for producing a radiation image conversion panel comprising the step (C) of forming a layer and the step (C) of forming a protective film, the compound represented by the general formula (1) and a europium compound are mixed as a phosphor raw material The relative humidity in the step (B) is 3 to 40%. Furthermore, the relative humidity in the step (A) is preferably 3 to 60%.

  If the humidity control in the step (B) is too high, moisture absorption of the powder is accompanied, so that the fluidity of the powder is lowered, and the brightness and sharpness may be lowered. It is assumed that the crystal structure of the phosphor is adversely affected. On the other hand, if the humidity is too low, the frequency of dust generation increases and the workability decreases with the generation of static electricity.

  If the humidity in the step (A) is too high, the brightness and sharpness may decrease as in the case where the humidity control in the step (B) is too high. In addition, if the humidity is too low, the frequency of dust generation is increased, and workability is reduced due to generation of static electricity.

(Phosphor base material)
Next, the compound represented by the general formula (1) according to the present invention will be described.

M ¹ represents at least one alkali metal atom selected from each atom such as Na, K, Rb and Cs, among which at least one alkaline earth metal atom selected from each atom of Rb and Cs is preferable. Preferably it is a Cs atom.

M ² represents at least one divalent metal atom selected from atoms such as Be, Mg, Ca, Sr, Ba, Zn, Cd, Cu, and Ni, and among them, Be, Mg, It is a divalent metal atom selected from each atom such as Ca, Sr and Ba.

M ³ is at least selected from each atom such as Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga and In. One kind of trivalent metal atom is represented, and among these, a trivalent metal atom selected from each atom such as Y, Ce, Sm, Eu, Al, La, Gd, Lu, Ga and In is preferred. is there.

  A is at least selected from each atom of Eu, Tb, In, Ga, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, Tl, Na, Ag, Cu, and Mg. One kind of metal atom.

  From the viewpoint of improving the stimulated emission luminance of the compound represented by the general formula (1), X, X ′ and X ″ each represent at least one halogen atom selected from F, Cl, Br and I atoms. At least one halogen atom selected from F, Cl and Br is preferred, and a Br atom is more preferred.

  In the general formula (1), when e> 0, the compound itself represented by the general formula (1) is a stimulable phosphor, which becomes a phosphor base material.

  In the general formula (1), when e = 0, specific examples of the compound represented by the general formula (1) according to the present invention will be given.

  (A) At least one compound selected from NaF, NaCl, NaBr, NaI, KF, KCl, KBr, KI, RbF, RbCl, RbBr, RbI, CsF, CsCl, CsBr and CsI is used.

_{(B) MgF 2, MgCl 2} , MgBr 2, MgI 2, CaF 2, CaCl 2, CaBr 2, CaI 2, SrF 2, SrCl 2, SrBr 2, SrI 2, BaF 2, BaCI 2, BaBr 2, BaBr 2 2H ₂ O, BaI ₂ , ZnF ₂ , ZnCl ₂ , ZnBr ₂ , ZnI ₂ , CdF ₂ , CdCl ₂ , CdBr ₂ , CdI ₂ , CuF ₂ , CuCl ₂ , CuBr ₂ , CuI, NiF ₂ , NiCl ₂ , NiBr _At least one or two or more compounds selected from ₂ and NiI ₂ compounds are used.

(Europium compound)
Examples of the europium compound used in the present invention include EuX ₂ , EuX ₃ and EuOX (X is a group consisting of F, Cl, Br, I and combinations thereof). Among them, EuBr ₃ , EuBr ₂ , EuCl ₂ and EuOBr gave excellent results.

(substrate)
The board | substrate of the radiation image conversion panel used for this invention is demonstrated.

  As the substrate used in the radiation image conversion panel of the present invention, various glasses, polymer materials, metals, etc. are used. For example, plate glass such as quartz, borosilicate glass, chemically tempered glass, cellulose acetate film, polyester, etc. Examples include films, polyethylene terephthalate films, polyamide films, polyimide films, triacetate films, polycarbonate resin and other organic resin films, metal sheets such as aluminum sheets, iron sheets, and copper sheets, or metal sheets having a coating layer of the metal oxide. .

  Among these, an organic resin film is preferable. The organic resin film is controlled by controlling the substrate temperature above the softening point, so that the deposited crystal can enter the substrate. Further, the amount of penetration can be controlled not only by the substrate temperature but also by the vapor incidence speed, vapor temperature, and the like. These incident speeds and temperatures can be controlled by the temperature at which the deposition material is evaporated.

(Vapor phase growth method of photostimulable phosphor)
In addition, the photostimulable phosphor layer according to the present invention is formed by a vapor deposition method. As a vapor phase growth method of the photostimulable phosphor, an evaporation method, a sputtering method, a CVD method, an ion plating method, or the like can be used.

  In the present invention, for example, the following methods can be mentioned.

In the vapor deposition method of the first method, after the substrate is first installed in the vapor deposition apparatus, the inside of the apparatus is evacuated to a degree of vacuum of about 1.333 × 10 ⁻⁴ Pa. Next, at least one of the photostimulable phosphor is heated and evaporated by a resistance heating method, an electron beam method, or the like, so that the photostimulable phosphor is grown on the substrate surface to a desired thickness. As a result, a photostimulable phosphor layer containing no binder is formed, but it is also possible to form the photostimulable phosphor layer in a plurality of times in the vapor deposition step.

  In the vapor deposition step, it is possible to co-evaporate using a plurality of resistance heaters or electron beams to synthesize the desired stimulable phosphor on the substrate and simultaneously form the stimulable phosphor layer. is there.

  After the vapor deposition is completed, a radiation image conversion panel according to the present invention is manufactured by providing a protective layer on the side opposite to the substrate side of the photostimulable phosphor layer as necessary. In addition, after forming a photostimulable phosphor layer on a protective layer, a procedure of providing a substrate may be taken.

  Furthermore, in the vapor deposition method, the vapor deposition target (substrate, protective layer or intermediate layer) may be cooled or heated as necessary during vapor deposition.

Further, the stimulable phosphor layer may be heat-treated after the vapor deposition. Further, in the above evaporation process, it may be carried out reactive deposition for depositing by introducing O _2, H ₂ etc. of the gas if necessary.

In the sputtering method as the second method, as in the vapor deposition method, a substrate having a protective layer or an intermediate layer is placed in a sputtering apparatus, and then the apparatus is evacuated to a vacuum of about 1.333 × 10 ⁻⁴ Pa. Then, an inert gas such as Ar or Ne is introduced as a sputtering gas into the sputtering apparatus to obtain a gas pressure of about 1.333 × 10 ⁻¹ Pa. Next, a stimulable phosphor layer is grown to a desired thickness on the substrate by sputtering using the stimulable phosphor as a target.

  Various applied treatments can be used in the sputtering process as in the vapor deposition method.

  The third method is a CVD method, and the fourth method is an ion plating method.

  Further, the growth rate of the photostimulable phosphor layer in the vapor phase growth method is preferably 0.05 to 300 μm / min. When the growth rate is less than 0.05 μm / min, the productivity of the radiation image conversion panel according to the present invention is poor, which is not preferable. On the other hand, when the growth rate exceeds 300 μm / min, it is difficult to control the growth rate, which is not preferable.

  When the radiation image conversion panel is obtained by the above-described vacuum deposition method, sputtering method or the like, since there is no binder, the packing density of the stimulable phosphor can be increased, and the radiation image conversion panel that is preferable in terms of sensitivity and resolution Is preferable.

  The film thickness of the photostimulable phosphor layer varies depending on the intended use of the radiation image conversion panel and the type of stimulable phosphor, but is 50 μm to 1 mm, preferably 100 to 100 μm from the viewpoint of obtaining the effects of the present invention. It is 800 micrometers, More preferably, it is 100-700 micrometers.

  In preparation of the photostimulable phosphor layer by the vapor phase growth method, the temperature of the substrate on which the photostimulable phosphor layer is formed is preferably set to 40 ° C. or higher, more preferably 80 ° C. or higher. Especially preferably, it is 100-400 degreeC.

(Sealing-protective film)
The protective film is for moisture-proofing the phosphor layer and suppressing deterioration of the phosphor layer, and is composed of a film with low moisture permeability. For example, a polyethylene terephthalate film (PET) can be used. Besides PET, a polyester film, a polymethacrylate film, a nitrocellulose film, a cellulose acetate film, a polypropylene film, a polyethylene naphthalate film, or the like can be used. Moreover, it can also be set as the structure which laminated | stacked several vapor deposition films which vapor-deposited metal oxide etc. on these films according to the moisture-proof property required.

  In addition, a fusion layer for fusing and sealing each other is formed on the surfaces of the phosphor plate facing each other on the substrate side and the phosphor layer side. As the fusion layer, a resin film that can be fused with a commonly used impulse sealer can be used. For example, an ethylene vinyl acetate copolymer (EVA), a polypropene (PP) film, a polyethylene (PE) film, etc. are mentioned, However, it is not restricted to this.

  It can be sealed by sandwiching the phosphor plate between the upper and lower protective films and fusing the end portions where the upper and lower protective films contact in a reduced-pressure atmosphere.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

Example 1
[Production of Radiation Image Conversion Panel 1]
1.7 g of europium oxide bromide (EuOBr) powder as a europium compound as an activator and 1000 g of cesium bromide (CsBr) powder as a phosphor matrix component were weighed and mixed in an environment with a relative humidity of 30%.

  Next, the phosphor material mixed in this way was placed in a resistance heating crucible and conditioned to a relative humidity of 20%.

Thereafter, the inside of the vapor deposition apparatus was evacuated to a high vacuum level, Ar gas was introduced, and the vacuum level was adjusted to 1.0 × 10 ⁻² Pa. Next, the resistance heating crucible was heated to vapor-deposit phosphor material at a rate of 2 μm / min, and CsBr: Eu stimulable phosphor was deposited. After vapor deposition, the inside of the apparatus was returned to atmospheric pressure, and the substrate was taken out from the apparatus. On the aluminum substrate, there was formed a phosphor layer (layer thickness: 150 μm) having a structure in which phosphor columnar crystals were densely planted in a substantially vertical direction.

  The phosphor plate thus obtained was fused and sealed using a moisture-proof protective film and the peripheral portion was sealed using an impulse sealer under reduced pressure to produce a radiation image conversion panel 1.

[Production of radiation image conversion panel 2]
In the production of the radiation image conversion panel 1, cesium iodide (CsI) was used instead of cesium bromide (CsBr), and the relative humidity in the steps (B) and (A) was changed as shown in Table 1. In the same manner, a radiation image conversion panel 2 was produced.

[Production of Radiation Image Conversion Panel 3]
In the production of the radiation image conversion panel 1, a photostimulable phosphor (CsBr: 0.0005Eu) was used instead of cesium bromide (CsBr), and the relative humidity in the steps (B) and (A) was as shown in Table 1. A radiation image conversion panel 3 was produced in the same manner except that the above was changed.

[Production of Radiation Image Conversion Panels 4-7]
Radiation image conversion panels 4 to 7 were produced in the same manner except that the relative humidity in the steps (B) and (A) was changed as shown in Table 1 in the production of the radiation image conversion panel 1.

[Evaluation]
The radiation image conversion panels 1 to 7 were evaluated as follows.

(Sharpness)
The sharpness of each produced radiation image conversion panel was evaluated by obtaining a modulation transfer function (MTF). The MTF applies a CTF chart to the radiation image conversion panel, irradiates the radiation image conversion panel sample with X-ray of 80 kVp for 10 mR (distance to the subject: 1.5 m), and then a semiconductor laser having a diameter of 100 μmφ (680 nm: panel Using a power of 40 mW), the CTF chart image was scanned and read. The values in the table are shown as the sum of 2.0 lp / mm MTF values. The obtained results are shown in Table 1.

(Luminance)
The brightness was evaluated using Regius 350 manufactured by Konica Minolta. As in the sharpness evaluation, X-rays were irradiated with a tungsten tube at 80 kVp and 10 mAs at a distance of 2 m between the bombardment source and the plate, and then a radiation image conversion panel was installed on the Regius 350 and read. Relative evaluation was performed based on the electrical signal from the obtained photomultiplier. The brightness of the radiation image conversion panel 7 was set to 1.0, and the other samples were represented by their relative values.

  It can be seen from Table 1 that the radiation image conversion panel according to the production method of the present invention is superior to the comparative radiation image conversion panel in both brightness and sharpness.

Claims (4)

Step (A) of mixing phosphor raw material, step (B) of taking the phosphor raw material in a resistance heating crucible and adjusting humidity, installing the resistance heating crucible in a vapor deposition apparatus, and forming a phosphor layer on the substrate by vapor deposition In the manufacturing method of the radiation image conversion panel which consists of the process (C) which forms, and the process (C) which forms a protective film, the mixture which mixed the compound and the europium compound which are represented by following General formula (1) as a fluorescent substance raw material is used. A method for producing a radiation image conversion panel, wherein the relative humidity in step (B) is 3 to 40%.
The general formula ^{(1) M 1 X · aM} 2 X '· bM 3 X ": eA
(In the formula, M ¹ is at least one alkali metal atom selected from Li, Na, K, Rb and Cs atoms, and M ² is Be, Mg, Ca, Sr, Ba, Zn, Cd, Cu. And at least one divalent metal atom selected from each atom of Ni, and M ³ is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, At least one trivalent metal atom selected from each atom of Tm, Yb, Lu, Al, Ga and In, and X, X ′ and X ″ are at least selected from each atom of F, Cl, Br and I 1 type of halogen atom, A is Eu, Tb, In, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, Tl, Na, Ag, Cu and Mg. At least one metal atom selected from each atom, and , B, e each represent a number between 0 ≦ a <0.5,0 ≦ b <0.5,0 ≦ e ≦ 0.2.) The method for producing a radiation image conversion panel according to claim 1, wherein the relative humidity in the step (A) is 3 to 60%. The method for producing a radiation image conversion panel according to claim 1, wherein M ^{1 in the} general formula (1) is Cs and X is Br. A radiation image conversion panel manufactured by the method for manufacturing a radiation image conversion panel according to claim 1.